Packet transmission service has been in use for some time and has traditionally been employed within communication systems such as wireless and wireline voice and/or data communications. Packet transmission service has also been used in association with digital communication systems which permit the efficient allocation of system resources via any of the well known access schemes, such as, for example, Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Code Division Multiple Access (CDMA) or any combination thereof. As will be appreciated, system resources may comprise radio frequency (RF) spectrum divided into communication channels to facilitate the transmission of user information.
In a packet transmission system, there are several access procedures a requesting unit can initiate when attempting to obtain and utilize system resources. These access procedures inform the system which type of operation a requesting unit is attempting to perform. Such operations include but are not limited to, call origination, location reporting, registration and page response.
The typical access procedure may be summarized as follows. A requesting unit transmits a system access request (request) over a request channel to a communications controller, starts a retry timer, and awaits a bandwidth grant message from the controller, informing the unit when and which channel is available for use to commence data tranmission. If the communications controller fails to respond to the request before the retry timer expires, the requesting unit will reissue the request (duplicate request). This procedure will continue until the requesting unit either receives a valid assignment of a resource (grant), reaches a maximum number of retries, or a packet lifetime timer expires, informing the requesting unit to cease.
Each request typically seeks from the communications controller sufficient communication resources to service a single packet of requesting unit information. As is known, a packet may require fragmentation (separation into a number of smaller portions) prior to being communicated over a relatively narrow bandwidth communication channel such as an RF communications channel. When packet fragmentation is employed, each access request will request those communication resources necessary to transmit all fragments associated with the to be delivered packet.
In an RF TDMA communication system, several requests may be received by the controller per TDMA frame. Typically these requests are sequentially stored (queued) in controller memory until TDMA resources (time slots) available to support transmission of the associated data packet fragments are allocated by the controller and communicated to a remote requesting device. For identification purposes, each request contains identification information which permits the controller to distinguish one remote unit's access requests from those of another. Requests, however, do not always arrive at the controller in the order as transmitted by the remote requesting device. This is due in part to the unpredictable nature of RF communication channels which are extremely sensitive to anomalies such as rayleigh fading, multipath and/or co-channel interference and other phenomenon which frequently result in, the inability to properly transmit and receive packetized information.
To improve information delivery reliability, retry timers may be employed to assure that lost corrupted or otherwise unintelligible transmissions are retransmitted in a timely fashion. While this methodology operates to improve the delivery of requesting unit requests, it is nonetheless susceptible to lengthy transmission delays. For example, when the controller receives out-of-order requests from a requesting unit, it will proceed to grant resources for those requests in the order as received. In return, the requesting device will transmit its data packet fragments to the controller utilizing the order in which grants are received from the controller. In those instances where the destination application can handle out-of-order fragments, the controller will communicate the data to the destination application with minimal delay. A problem arises, however, when the destination application can not handle out-of order fragments (i.e., data). In such instances, the out-of-order data must be stored until all fragments associated with the original data packet have been received and assembled in the proper order. Then and only then may the controller communicate the data to the destination application. As will be appreciated, the time required (delay) for out-of-order data packet fragments to be transmitted to the controller and reassembled prior to delivery presents a severe limitation upon overall system throughput.
It would be extremely advantageous, therefore to provide an improved time-out retransmit methodology of data packet transmission which decreased the delays associated with receipt of out-of-order data packet transmissions in a packet transmission communication system.